----- Submission 1 (Thu May 11 15:25:21 GMT 2006) ----- Assigned ID: 297 ----- Submission 1 (Fri Jan 27 17:59:36 GMT 2006) ----- M82 as a Fossil Starburst: Probing the Super Star Cluster Content of Region B The importance of M82 as a benchmark for starburst studies has been recognised by the STScI-sponsored ACS/WFC mosaic of M82 in the B, V, I and H alpha filters. This proposal supplements this unique legacy dataset by obtaining U-band observations (F330W filter) of the fossil starburst region B in M82. This region is rich in compact intermediate age (~ 1 Gyr) star clusters. The combination of U-band photometry with the ACS/WFC STScI BVI survey and archival NICMOS JH data will allow us to derive accurate ages, luminosities and masses for this rare population of intermediate age massive star clusters. The U-band is essential for determining ages of clusters < 2 Gyr old because it measures the depth of the Balmer jump. We will use these data to determine the true shape of the cluster luminosity function (CLF) for the M82-B fossil starburst region and thus address the question of whether young massive clusters will eventually become globular clusters.
We have chosen the ACS/HRC camera in preference to WFPC2 because the proposed dataset will complement the few U-band observations of M82 (A, C, F) that exist which have all been obtained with ACS/HRC. The HRC also has the advantage that the light profiles of the clusters in M82 will be much better defined than the PC because of the smaller pixel size. At the distance of M82, 1 HRC pixel approximately equals 0.5 pc compared to a typical cluster diameter of 6 pc. To calculate exposure times, we are guided by the study of M82-B by de Grijs et al. (2001, AJ, 121, 768) which reached a 50% completeness limit at V of 22.5 mag. This translates to a mass of 50,000 solar masses for a 1 Gyr old cluster which is a factor of two deeper than the mass corresponding to the peak of the globular cluster mass function at 10^5 solar masses. In fact, we expect to go deeper than this because the STScI BVI mosaic of M82 will reach fainter V magnitudes than those of de Grijs et al. (2001). The extinction in region B is variable; from previous studies, we adopt an upper limit of E(B-V)=1.0. This will ensure that we go deep enough at U to match the new, deeper ACS BVI data. With the F330W filter and an A7V spectral type (appropriate for a cluster with an age of ~ 1 Gyr), a S/N of 10 is reached in 130 min for V=22.5. To cover region B with HRC, we will use two separate pointings; M82-B1 and M82-B2. We therefore require a total exposure time of 260 min. The exposures will be broken down into sub-exposures and will be acquired using the ACS dither-line pattern to remove hot pixels. None None None UNRESOLVED STELLAR POPULATIONS 12 false 0.0 false false false false false SUPPORTED GALAXY STARBURST J2000 09 56 2.6950 +69 41 10.05 J2000 GALAXY STARBURST J2000 09 55 57.1950 +69 41 6.35 J2000 ACS/HRC Imaging No No F330W ACS/HRC Imaging No No F330W POS-TARG DITHER 0.198 LINE false false 3 44.28 ACS-HRC-DITHER-LINE 1 false /private/tmp/OPVisit37666.xml None (Tic-Visit :proposal-id 10853 :visit-id "01" :proposal-version -1 :trans-version "20060322" :date "11-May-2006 16:05:55.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 3 :saa-model "27" :si-bright-earth-limb-angle 20.0 :data-volume 858816 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 10853 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 10853 :visit-id "01" :orbit-number 1 :pcs-time 355 :si-vis-utilization 2926 :al-overhead-at-end 0 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3281 :pcs-gap 0 ) (Tic-Orbit :proposal-id 10853 :visit-id "01" :orbit-number 2 :pcs-time 355 :si-vis-utilization 2844 :al-overhead-at-end 0 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3281 :pcs-gap 0 ) (Tic-Orbit :proposal-id 10853 :visit-id "01" :orbit-number 3 :pcs-time 355 :si-vis-utilization 2824 :al-overhead-at-end 0 :internal-dur-at-end 351 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3281 :pcs-gap 0 ) true 3 0 /private/tmp/OPVisit37667.xml (Tic-Visit :proposal-id 10853 :visit-id "02" :proposal-version -1 :trans-version "20060322" :date "11-May-2006 16:06:00.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 3 :saa-model "27" :si-bright-earth-limb-angle 20.0 :data-volume 858816 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 10853 :visit-id "02" :obset-id "02" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 10853 :visit-id "02" :orbit-number 1 :pcs-time 355 :si-vis-utilization 2926 :al-overhead-at-end 0 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3281 :pcs-gap 0 ) (Tic-Orbit :proposal-id 10853 :visit-id "02" :orbit-number 2 :pcs-time 355 :si-vis-utilization 2844 :al-overhead-at-end 0 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3281 :pcs-gap 0 ) (Tic-Orbit :proposal-id 10853 :visit-id "02" :orbit-number 3 :pcs-time 355 :si-vis-utilization 2824 :al-overhead-at-end 0 :internal-dur-at-end 351 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3281 :pcs-gap 0 ) true 3 0